1. Technical Field
This application relates to UMTS (Universal Mobile Telecommunications System) in general, and to an apparatus and method for implementing broadcast system information changes.
2. Description of the Related Art
The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In a typical cellular radio system, mobile user equipment (UE) communicates via a radio access radio network (RAN) to one or more core networks. User equipment (UE) comprises various types of equipment such as mobile telephones (also known as cellular or cell phones), lap tops with wireless communication capability, personal digital assistants (PDAs) etc. These may be portable, hand held, pocket sized, installed in a vehicle etc and communicate voice and/or data signals with the radio access network.
The radio access network covers a geographical area divided into a plurality of cell areas. Each cell area is served by at least one base station, which may be referred to as a Node B. Each cell is identified by a unique identifier which is broadcast in the cell. The base stations communicate at radio frequencies over an air interface with the UEs within range of the base station. Several base stations may be connected to a radio network controller (RNC) which controls various activities of the base stations. The radio network controllers are typically connected to a core network.
UMTS is a third generation public land mobile telecommunication system. Various standardization bodies are known to publish and set standards for UMTS, each in their respective areas of competence. For instance, the 3GPP (Third Generation Partnership Project) has been known to publish and set standards for GSM (Global System for Mobile Communications) based UMTS, and the 3GPP2 (Third Generation Partnership Project 2) has been known to publish and set standards for CDMA (Code Division Multiple Access) based UMTS. Within the scope of a particular standardization body, specific partners publish and set standards in their respective areas.
Consider a wireless mobile device, generally referred to as user equipment (UE), that complies with the 3GPP specifications for the UMTS protocol. The 3GPP 25.331 specification, v. 3.15.0, referred to herein as the 25.331 specification, addresses the subject of UMTS RRC (Radio Resource Control) protocol requirements between the UMTS Terrestrial Radio Access Network (UTRAN) and the UE.
Clause 8.1.1 of the 25.331 specification, relates to the broadcast of system information. The UTRAN sends system information to a UE by means of a message that comprises a Master Information Block (MIB) and a plurality of System Information Blocks (SIBs). The MIB provides references and scheduling information for a number of system information blocks. A system information block groups together system information elements (IEs) of the same nature. Different system information blocks may have different characteristics, e.g. regarding their repetition rate and the requirements on UEs to re-read the system information blocks. The system information blocks contain the actual system information. The master information block may optionally also contain reference and scheduling information to one or two scheduling blocks, which give references and scheduling information for additional system information blocks. Scheduling information for a system information block is included in either the master information block or one of the scheduling blocks.
When a UMTS cell is selected by a mobile device, the master information block (MIB) is read on the broadcast control channel (BCCH) followed by the appropriate system information blocks (SIBs).
The Paging CHannel (PCH) channel needs to be setup by the mobile device if in Idle, Cell_PCH, or URA_PCH state. Information required to configure the PCH is included in system information block type 5 (SIB5).
If the Universal Terrestrial Radio Access Network (UTRAN) needs to change any of the system information blocks, it informs the mobile devices (UEs) in the cell. This is achieved by the UTRAN sending SYSTEM INFORMATION as illustrated generally in FIG. 1. As illustrated in FIG. 2, for UEs in Idle, Cell_PCH, or URA_PCH states, a PAGING TYPE 1 message (with the information element ‘BCCH modification info’ included) is sent via PCH to alert a UE that there is a change in system information. A separate mechanism is used to alert a UE in Cell_FACH if there is a change in system information. This entails using a SYSTEM INFORMATION CHANGE INDICATION message sent on one or more Forward Access CHannels (FACHs) (as illustrated in FIG. 3).
There is a problem in that a PAGING TYPE 1 message sent after the cell is selected but before the UE has configured the PCH will be missed. For UEs in Cell_FACH state, a SYSTEM INFORMATION CHANGE INDICATION message sent after the cell is selected but before the UE has configured the FACH will also be missed.
In these cases, the UE will be using incorrect/out-of-date system information blocks. This could cause the UE to be unusable in the current cell or have other undesirable effects.
An additional case is where the PAGING TYPE 1 or SYSTEM INFORMATION CHANGE INDICATION message indicates a system information change will occur at a specific time (up to 4096 frames or 40.96 seconds in the future). The SIBs are transmitted by the UTRAN in a cycle which repeats every 4096 frames (40.96 seconds). Here, if the UTRAN sends these messages before the UE selects the cell, the system information change will again be missed by the UE.
There are thus proposed strategies for dealing with the broadcast of system information. A number of such strategies are detailed below.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of an apparatus and method for handling the broadcast of system information in UMTS.
The same reference numerals are used in different figures to denote similar elements.